Process and apparatus for fabricating optical fiber cables

Abstract

A process and apparatus for fabricating an optical fiber communication cable are described herein. The optical fiber cable has a cable core including a metal containment tube and at least one optical fiber within the tube. The containment tube preferably is formed by drawing a strip of metal through at least one forming die. In a first aspect of the present invention, smooth operation of the forming die is promoted by first passing the metal strip through a shaving die to remove any shearing burrs along the strip edges and to maintain the width of the strip within a desired tolerance. In a second aspect of the present invention, various approaches for effectively sealing the containment tube are described. In a first embodiment, the tube is sealed using a wave soldering approach wherein a flow of moving molten solder is used to substantially fill a seam in the tube. In a preferred embodiment, a mechanical separation is placed between the tube and the moving molten solder to prevent sealing until a steady state running condition has been achieved. In a second embodiment, the tube is sealed by wrapping a metal foil having a meltable coating about the tube and heating the assembly to melt the coating and effect a seal. In a third aspect of the present invention, the optical fiber cable is provided with an improved concentricity. The improved concentricity is effected by passing the sealed metal tube through a die for removing any excess material such as solder from about the outer periphery of the tube.

We claim: 
     
       1. An apparatus for fabricating an optical fiber cable, said apparatus comprising: means for assembling a cable core having a metal containment tube and at least one optical fiber within said tube, said core assembly means including means for forming a strip of metal into said tube, wherein the improvement comprises:   means for providing said strip to said forming means in a substantially burr-free condition and with a width that does not exceed a desired width, said strip providing means comprising a shaving die having a bore through which said strip passes, said bore having a diameter substantially equal to said desired width,   whereby providing said strip in said substantially burr-free condition and with said width not exceeding said desired width promotes smooth operation of said tube forming means.   
     
     
       2. The apparatus of claim 1 wherein said shaving die shapes said strip to have a desired cross-sectional configuration. 
     
     
       3. The apparatus of claim 1 further comprising: means for guiding said strip through the approximate center of said bore.   
     
     
       4. The apparatus of claim 3 wherein said guiding means comprises: a first rotatable member adjacent an entry face of said die; and   a second rotatable member adjacent an exit face of said die.   
     
     
       5. The apparatus of claim 4 wherein said strip guiding means further comprises: means for guiding the edges of said strip so that said strip is laterally aligned with said bore.   
     
     
       6. The apparatus of claim 5 wherein said edge guiding means comprises: a pair of collars mounted on each of said rotatable members.   
     
     
       7. The apparatus of claim 6 further comprising: said die being mounted in a support structure;   each said rotatable member being mounted to said support structure by a pair of mounting arms; and   each said arm having a bearing in which an end of one of said rotatable members rotates.   
     
     
       8. A process for fabricating an optical fiber cable, said process comprising: providing means for forming a strip of metal into a tube;   passing said strip through said forming means to form said tube; and   inserting at least one optical fiber into said tube,   wherein the improvement comprises:   passing said strip through a shaving die having a bore with a diameter substantially equal to a desired strip width prior to said tube forming step so as to promote smooth operation of said forming means by providing said strip to said forming means in a substantially burr-free condition and with a width that does not exceed said desired strip width.   
     
     
       9. The process of claim 8 further comprising: guiding said strip through the approximate center of said bore.   
     
     
       10. The process of claim 9 further comprising: guiding the edges of said strip so that said strip is laterally aligned with said bore.   
     
     
       11. The process of claim 8 further comprising: said step of passing said strip through said die further comprising shaping said strip to have a desired cross-sectional configuration.   
     
     
       12. The process of claim 11 further comprising: said forming means being at least one forming die;   said tube forming step comprising drawing said strip through said at least one die; and   said shaping step comprising shaping said strip to have a substantially trapezoidal cross section,   whereby drawing forces created during said tube forming step are reduced by said strip shaping.